Effect of methanolic extracts of Tectona grandis linn leaves on diabetic neuropathy in streptozotocin‒induced diabetic rats

Abstract

Tectona grandis (TG) plant belonging to family Verbenaceae, it is medicinally reported and claims to cure various diseases in Indian traditional system (Ayurveda) and in folklore. The purpose of this study is to examine the methanol extract of Tectona grandis leaves (TGME) in Streptozotocin (STZ) induced diabetic neuropathy in rat. Initially acute oral toxicity study of TGME was carried out in rats to evaluate the dose for animal study. STZ (45mg.kg‒ 1) was used to induce diabetes in rats. TGME was given orally dose of 250 and 500mg.kg‒ 1 to normal and diabetic rats from initiate 7th to 8th weeks (total 14 days). Blood collection for estimation of glucose level, biochemical parameters and behavioural parameters were assessed initially up to 8th week (every 2nd week interval). At the end of study (after 8th week) rats were sacrificed for estimation brain tissue estimations and histopathology of rat paw skin was also carried out. In acute oral toxicity study result, TGME do not cause any toxicity or death in animals. Diabetic rat’s significant increase in serum glucose and other biochemical parameters as well as mechanical allodynia was indicates hyperalgesia after 2weeks of diabetes induction. Brain tissue estimations revealed increase in lipid peroxidation (LPO) level, a decrease in antioxidant parameters and histopathology study of paw skins of rat’s intraepidermal nerve fiber density was decreased in diabetic neuropathy STZ treated group. Administration of dose of 250 and 500mg.kg‒ 1 of TGME significantly (P<0.001) decreased blood glucose level in normal and diabetic rats. A dose of 500mg.kg‒ 1 significantly (P<0.01 and P<0.001) increases the tail withdrawal latency with hot and cold water tail immersion tests respectively. Both the doses of TGME significantly increase the level of glutathione (GSH) and lower the levels of LPO, catalase (CAT) and superoxide dismutase (SOD). Histopathology study of paw skin of rat intraepidermal nerve fiber density was increased as a result of drug administration. The results concluded that TGME possesses potential to combat glucose; hypolipidemic effect and scavenge free radicals in diseases associated with oxidative stress, suggests its role in preventing diabetes‒related complications.